Support device for machining workpieces

ABSTRACT

Support device for machining workpieces comprising three parts, namely : a fixed bed, a saddle slidable on the bed in a first direction, a chassis pivotable on the saddle about a first axis orthogonal to the first direction and a table rotatable on the chassis about a second axis orthogonal to the first axis. Means are provided for relatively moving the three parts. Locking means maintain the parts in given positions relative to each other. Weight compensating means are interposed between the saddle and bed and between the table and chassis for compensating variations in the forces exerted by the workpiece on the bed and on the chassis in different regions, for example due to an overhanging position of the workpiece relative to the chassis or bed.

United States Patent Pillot et a].

[ 5] Nov. 28, 1972 SUPPORT DEVICE FOR MACHINING WORKPIECES [72]Inventors: Maurice Pillot, Etupes; Louis Kilian,

Montbeliard, both of France [22] Filed: July 28, 1970 [21] Appl. No.:58,844

[30] Foreign Application Priority Data Aug. 1, 1969 France ..6926560[52] US. Cl. ..90/58 C, 308/6 R [51] Int. Cl. ..B23q 1/04 [58] Field ofSearch ..90/58 R, 58 C; 308/6 R;

[56] References Cited UNITED STATES PATENTS 3,293,990 12/1966 Deflandre..90/58 R 2,526,518 10/1950 Turrettini ..308/6 R 3,443,310 5/1969Burroughs et al. ..29/568 3,203,314 8/1965 Ried ..90/58 R X 3,345,78210/1967 Thompson ..308/6 R X v 450 I 21 1 1% l l 11! G 1 Li 23 5 -1 0 iiFOREIGN PATENTS OR APPLICATIONS 1,119,472 6/1956 France ..90/58 R683,055 11/1952 Great Britain ..90/58 R Primary Examiner--Andrew R.Juhasz Assistant ExaminerZ. R. Bilinsky Att0mey--Burns, Doane, Benedict,Mathis Swecker and ABSTRACT Support device for machining workpiecescomprising three parts, namely a fixed bed, a saddle slidable on the bedin a first direction, a chassis pivotable on the saddle about a firstaxis orthogonal to the first direction and a table rotatable on thechassis about a second axis orthogonal to the first axis. Means areprovided for relatively moving the three parts. Locking means maintainthe parts in given positions relative to each other. Weight compensatingmeans are interposed between the saddle and bed and between the tableand chassis for compensating variations in the forces exerted by theworkpiece on the bed and on the chassis in different regions, forexample due to an overhanging position of the workpiece relative to thechassis or bed.

23 Claims, 9 Drawing Figures FIG.6

SHEET 3 0F 5 PATENTEMuvzs I972 PATENTEDHHV28 I 1 Sum of 5 3.70384?PIC-3.8

PATENTEDNUV 28 I972 SHEET 5 [IF 5 SUPPORT DEVICE FOR MACHININGWORKPIECES The present invention relates to machine tools and concernsmore particularly support devices for workpieces to be machined.

It is frequently necessary to machine by means of machine tools of forexample the boring and milling, milling and boring, milling and planingor copying milling type,workpieces, such as presstool dies for blankingor forming or press frames, having a weight of as much as 25 metrictons. The mounting and positioning of workpieces of such size present anumber of problems which known support devices have been unable to solvein a satisfactory manner.

These support devices comprise a roughly horizontal platform on whichare placed movable squares or brackets which define a positioning planewhich is roughly orthogonal to the spindle of the machine tool, and arotary table having a vertical axis allowing the direct clamping of theworkpiece or the positioning of squares supporting this piece.Consequently, it is necessary, in order to machine the workpiece in itsvarious planes, to mount it either on the squares or on the rotary tableand this requires dismounting and transfers involving considerable anddifficult handling owing to the weight of the workpieces.

An object of the invention is therefore to provide a support device forworkpieces which overcomes the drawbacks of known devices.

The support device for workpieces to be machined comprises a fixed bed,a saddle mounted on said bed to be slidable in a first direction, achassis mounted on the saddle to pivot about a first axis roughlyorthogonal to said first direction, a table mounted on said chassis tobe rotatable about a second axis roughly orthogonal to the axis of saidchassis, means for effecting each of said relative movements and lockingmeans for maintaining the various parts of the device in a givenposition relative to each other.

The combination of these various movements enables the workpieces to beshifted or fed relative to the tool without necessity to transfer ordismount them so that it is possible to machine all their faces exceptthe face by which they are fixed.

Further features and advantages of the invention will be apparent fromthe ensuing description with reference to the accompanying drawings.

In the drawings:

FIG. 1 is a diagrammatic assembly view in elevation of the deviceaccording to the invention and an associated machine tool;

FIG. 2 is a plan view, with a part cut away, of the device shown in FIG.1;

FIG. 3 is a sectional view, taken along line 3-3 of FIG. 1, showing howthe saddle is mounted on the bed, it being offset to show the variousmechanisms provided between the saddle and the bed;

FIG. 4 is a sectional view, taken along line 4-4 of FIG. 1, showing howthe pivotable chassis is mounted on the saddle;

FIG. 5 is a sectional view, taken along line 5-5 of FIG. 1, showing howthe table is mounted on the chassis, it being offset to show the variousmechanisms provided between the table and the chassis;

FIG. 6 is a diagram representing the hydraulic supply circuit for theunlocking and lightening means between the saddle and the bed;

FIG. 7 is a diagram representing the hydraulic supply circuit for theunlocking and lightening means and the weighting means between the tableand the chassis;

FIG. 8 is a diagram representing the hydraulic control circuit forpivoting the chassis relative to the saddle, and

FIG. 9 is a general diagram of the hydraulic circuit of the device.

FIG. 1 shows a machine tool A and a support device B,according to theinvention,placed on a platform C constituted by a concrete block. Themachine tool A can be, as indicated hereinbefore, a boring-milling, aplaning-milling, or a reproducing milling machine or any other machinetool.

The support device B for the workpieces to be machined comprises fourmain parts, namely a bed D, a carriage or saddle E, a chassis F and atable G. The saddle E is mounted on the bed D to be slidable in ahorizontal direction X-X. The chassis F is mounted on the saddle E to bepivotable about a horizontal axis Y Y, orthogonal to the direction X-X.The table G is mounted on the chassis F to be pivotable about an axisZ-Z perpendicular to the plane of the chassis and orthogonal to the axisY-Y.

The various possible movements of the tool-carrying head of the machineA are conventional and have not be illustrated in the drawing.

There will now be described in more detail the construction of the mainparts constituting the device according to the invention and the mannerin which they are assembled. The control devices controlling themovements, the locking and the lightening will be described later.

As can be seen in FIG. 3, the bed D is adapted to support the whole ofthe device and guide the saddle E in its travel in the direction X-X.This bed is directly secured to the ground in a concrete block C by rods1 and screwjacks 2 whereby the bed can be set in a perfectly horizontalplane.

The cast iron bed has strengthening ribs and defines slideways 3 onwhich the saddle E bears, this saddle carrying on the face 4 thereof incontact with the slideways a bronze fitting 5. The bed D also carriestwo strips 6 of hardened steel the lateral faces 6 of which co-operatewith rolling bearings 7 which act as guides and are mounted oneccentrics and carried by the lower wall 4 of the saddle E. Theseadjustable guide rolling bearings permit an exact centering of thesaddle and ensure with high precision the orthogonal relationshipbetween the axis Y-Y and the direction of travel X-X. These guiderolling bearings also permit the adjustment of the prestressing of thelateral guiding of the saddle relative to the bed.

It will beseen from FIGS. 1 and 2 that the slideways 3 are protected bytelescopic sheets 8 which however allow access to the slideways. The bedD carries, in the median part thereof as concerns both the longitudinaland transverse directions, a fixed nut 9 which coperates with aleadscrew l0 driven in rotation by a servomotor 11 (shown in theassembly diagram in FIG. 9), this assembly causing the saddle to moverelative to the bed.

There will now be described, with reference to FIG. 4, the manner inwhich the chassis F is mounted on the saddle E for pivotal movementabout the axis Y-Y. The saddle E carries in its upper part a fixed shaft12 carrying at both ends rolling bearings 13 having tapered rollerswhich are arranged in pairs in opposed relation. The shaft 12 is mountedin two supports 14, 15, having tapered inner bearing faces 14a, 150, soas to achieve a particularly rigid assembly. The shaft has a taperedshape in the part 12a thereof in the region of the support 4, this shapecorresponding to the inner shape of the support. To facilitate itsdisassembly, the shaft has a cylindrical shape in its part 12b betweenthe two supports and in the region of the support 15. A tapered bushing16 is interposed between the part 12b of the shaft and the tapered innerbearing face of the support 15, it being fixed to the support 15 byreleasable fixing means (not shown). The outer rings of the four rollingbearings 13 are integral with sleeves l7, l8 fixed to the chassis F. Twobearing faces 19, 20 provided at the ends of the shaft constitutereference faces for aligning with precision the pivot axis Y--Y of thechassis on the saddle. The shaft 12 carries at the right end thereof (asviewed in FIG. 4) an index or pointer 21 which co-operates with agraduation carried by a plate 22 integral with the chassis. This indexaffords a first indication of the value of the pivot angle of thechassis.

As can be partly seen in FIGS. 1, 2, 4 and 5, the chassis F comprises aplatform 23 and two side walls 24 which are disposed on each side of thesaddle E. The platform 23 defines a support or guide face 25 which isroughly horizontal when viewed in FIG. 1 and on which the table G ismounted to rotate about the axis ZZ. This table is connected to thechassis by pivot means 26 comprising a large-size rolling bearing whichtakes up play or clearance (FIG. a guide strip 27 and four retainingelements, such as 28.

The table carries a gear wheel having internal teeth 29 which is part ofthe mechanism for rotating the table about the axis ZZ. The gear wheel29 carries a ring 30 of hardened steel which cooperates with alightening device adapted to counter the effect of the weight of theworkpiece,which will be described hereinafter. The table G comprises inthe known manner T-slots 31 for clamping the workpiece to be machined.

There will now be described the various control devices for producingthe various relative movements, the locking and possibly the lighteningbetween respectively the saddle E and the bed D, the chassis F and thesaddle E, and the table G and the chassis F.

The saddle E is made to move relative to the bed in the direction X-X bya servomotor 11 which drives the leadscrew as indicated hereinbefore.This mechanism is provided for feeding the workpiece at rates which arevariable as desired within two ranges a rapid feed of 90-3,600 mm perminute or a slow feed of 1.2-410 mm per minute (namely 0.02 mm persecond). The saddle can be positioned relative to the bed in incrementsof minimum value of the order of 0.006 mm.

The means for locking the saddle relative to the bed in a given positionare shown in FIGS. 3 and 6. These means comprise four adjustablehydraulic jacks 32 having a cylinder 32a carried by the saddle and apiston rod constituting a pull rod 32b received in a T-slot 33.

These jacks normally apply the saddle against the bed under the actionof resiliently yieldable means (not shown) and unlock or release thesaddle when fed with fluid under pressure. The position of these fourfluid jacks 32 in plan can be seen in FIG. 6.

A lightening device is also provided between the saddle and the bedwhich in particular compensates the forces exerted by the loadconstituted by a workpiece especially according to the position of thepivotable chassis and of the work-carrying table. This device comprisesfive pairs of fluid jacks 34, 35, 36,37,38 whose positions in plan areshown in FIG. 6, the cylinder of each jack, for example the cylinder34a, being carried by the saddle E (FIG. 3). The piston rod, such as34b, of these jacks constitutes a fork carrying a rolling bearing 39which has a horizontal axis of rotation and bears against a rolling faceconstituted by the upper face 6b of the hardened steel strip 6.

The unlocking jacks 32 and the compensating jacks 34 to 38 are fed withfluid under pressure by way of a conduit 40 (FIG. 6), directly asconcerns the jacks 32, and through a pressure reducer 41 and anelectrically controlled distributing valve 42 having three positions asconcerns the motors 34 to 38. A pressure gauge 43 is provided in thesupply conduit of the jacks. The position of the slide of the slidevalve is controlled through two electromagnets 42a, 42b by two positiondetectors 44, 45 shown in FIG. I mounted on the saddle and actuated bythe pivotable chassis. This control device is incorporated in thegeneral hydraulic circuit shown in FIG. 9 and will be described in moredetail hereinafter.

The mechanism for pivoting the chassis F with respect to the saddle Ecomprises, disposed symmetrically on each side of the saddle, twohydraulic jacks 46 whose cylinders 46a are integral with the saddle andwhose piston rods 46b are connected to the chassis. These two jacks aresupplied with fluid in accordance with the hydraulic diagram shown inFIG. 8.

The jacks 46 are controlled by a conduit 47 through two circuitsconnected in parallel, namely a high-flow circuit 48 pertaining to rapidfeed and a variable lowflow circuit 49 for positioning. The rapid feedcircuit comprises a three-position distributing valve 50 having anelectric control. The chambers 51 of the jacks 46 are connected to thevalve 50 through a path which comprises, connected in parallel, anelectrically controlled adjustable retaining valve 52 and a check valve53 and two check valves 54, 55 which are pilot controlled and directlyconnected to the jacks and ensure that the circuit is safe and perfectlysealed.

The other chambers 56 of the jacks 46 are connected to the distributingvalve 50 through a path which comprises, connected in parallel, anadjustable retaining valve 57 having an electric pilot control and acheck valve 58 and two piloted check valves 59 and 60. The pilot controlof the valves 52, 57 is effected by two position detectors 44, 45mounted on the saddle and actuated by the'chassis when it pivots.

The low-flow positioning circuit 49 comprises mainly a flow regulator 61controlled electrically, a three-position rapid-response distributingvalve 62 controlled electrically which directs the flow of fluiddirectly to the chambers 51 and 52 of the jacks 46 behind the pilotedcheck valves 54,55-59,60 respectively. A box 63 having piloted checkvalves at the outlet of the distributing valve ensures that thepositioning circuit 49 is perfectly sealed.

Locking means (FIGS. 1 and 2) are provided between the chassis and thesaddle. The side walls 24 of the pivotable chassis each comprises ontheir inner face four T-slots 64 which extend along arcs of a circlecentered on the pivot axis Y-Y. The saddle carries on its upper face twogroups of four fluid jacks 65 whose cylinders 65a are integral with thesaddle and whose piston rods 65b constitute pull rods whose ends arereceived in the T-slots 64. As in the case of the locking between thesaddle and the bed, these rods, when actuated by resiliently yieldablemeans (not shown), normally lock the chassis with respect to the saddle,unlocking or release being achieved when fluid under pressure issupplied thereto.

The work-carrying table G is rotated about the axis ZZ by a servomotor66 which drives a leadscrew or worm meshed with a worm wheel having avertical axis, this wheel being integral with a gear wheel which ismeshed with the gear wheel 29 having internal teeth. This mechanismcomprises a device for taking up play in the teeth and is conventionaland therefore has not been shown in detail.

A locking mechanism similar to that between the saddle and the frame(FIG. 5) is provided between the table G and the chassis F. Thismechanism comprises four fluid jacks 67 whose positions in plan areindicated in FIG. 7. The cylinders 67a of these jacks are integral withthe chassis and their piston rods constitute pull rods 67b engaged incircular T-slots 68 provided in the lower part of the table. These rodsnormally lock the table relative to the chassis, unlocking or releasebeing achieved only when the jacks 67 are fed with hydraulic fluid underpressure.

A lightening or compensating device, similar to that between the saddleand the bed (FIGS. 5 and 7), is provided between the table G and thechassis F. This compensating device comprises two pairs of jacks 69, 70whose positions in plan are shown in FIG. 7. The cylinders of thesejacks such as the cylinder 69a shown in FIG. 5, are integral with thechassis and their piston rods 69b constitute forks in which are mountedfor rotation about horizontal axes roller or needle bearings 71 whoseouter ring can be brought in contact with the hardened steel ring 30carried by the gear wheel 29 of the table. Further, two jacks 72 efiectan opposite compensation, namely a weighting, whose purpose will beexplained hereinafter, and act on a ring of hardened steel 73 through alever 74 (which doubles the force exerted) and a needle bearing 75.

The unlocking jacks 67, the compensating jacks 69, 70 and thecompensating jacks 72 are supplied with fluid under pressure inaccordance with the diagram shown in FIG. 7 by a conduit 76, directly asconcerns the jacks 67, and through a pressure reducer 77 and athree-position distributing valve 78 having an electric control asconcerns the jacks 69, 70 and 72. The distributing valve 78 has twoelectromagnets 78a, 78b and is controlled by the two position detectors44, 45 actuated by the chassis. A pressure gauge 79 is also provided.

The general diagram of the hydraulic circuit of the device according tothe invention will now be described with reference to FIG. 9. Thishydraulic circuit comprises a tank 79, a pump 80 driven by a motor 81and supplying a main conduit 82 with hydraulic fluid under pressure. Twofilters 83, 84 are respectively provided on the inlet side and outletside of the pump 80. A discharge valve 85 is provided on the outlet sideof the pump and permits excess fluid to return to the tank by way ofanother filter 86. Connected to the main con-. duit 82 in parallel arethree conduits 87, 88, 89 which respectively supply the circuits 90, 91,92 corresponding to the feeding of the saddle with respect to theframe,the rotation of the table with respect to the chassis and thepivotal movement of the chassis with respect to the saddle. These threecircuits are very similar in design, as can be seen in the diagram shownin FIG. 9.

Each of the three circuits 90, 91, 92 connected in parallel supplies thedrive mechanism, the unlocking mechanism, and possibly the compensatingmechanism of each assembly, namely the saddle-bed assembly, thechassis-saddle assembly and the table-chassis assembly. The circuitcomprises an electrically-controlled two-position selecting valve 93returned by spring and pressure which is normally in the position shownin the drawing in which there is no supply to the rest of the circuit.Downstream of this valve is a sequence valve or pressure regulatingvalve 94 which stops the pressure so that, when the latter reaches agiven value, the unlocking fluid jacks 32 and the pressure reducer 41 ofthe compensating jacks are supplied with fluid. Downstream of thissequence valve 94 is a distributing valve 95 connected to the servomotor11 which controls the feed of the saddle with respect to the frame.Connected between the selecting valve 93 and the sequence valve 94 is amanostat 96 which is adapted to measure and signal the pressure and thenauthorize operation of the servomotor 11 when the pressure reaches. asufficient value. This manostat constitutes safety means.

The maximum feed of the saddle with respect to the bed is deter-ruinedby two position detectors 97, 99 which co-operate with cams 99, 100(FIG. 1). The circuit 91 which controls the rotation of the table com--prises an electrically-controlled two-position selecting valve 101 whichin its normal position cuts off the supply of the circuit 91; a sequencevalve 102 which establishes in the circuit a given pressure sufficientfor supplying the unlocking jacks 67 and the pressure reducer 77 of thecompensating jacks 69, 70 and compensating jacks 72; a distributingvalve 103 connected to the servomotor 66 which controls the rotation ofthe saddle; and a manostat 104 which is adapted to measure and signalthe pressure and authorize actuation of the servomotor 66.

The circuit 92 which controls the pivoting of the chassis comprises anormally-closed two-position selecting valve 105; a sequence valve 106which establishes a given pressure in the circuit sufficient to actuatethe unlocking jacks 65; and a manostat 107 which performs the samefunction as the manostats 96 and 104 and authorizes the actuation of thedistributing valves 50, 62 respectively controlling the circuits foreffecting the rapid feed and the positioning of the chassis with respectto the saddle.

This assembly is completed by a control unit which will not be describedin the present description.

There will now be described the operation of the device according to theinvention, and in particular the movements of the various partsconstituting this device, from a position in which these various partsare rendered integral by the various locking mechanisms.

There will first be described the feeding of the saddle E with respectto the frame D with reference in particular to FIGS. 3, 6 and 9. Toeffect such a movement, the selecting valve 93 is energized (FIG. 9) soas to put it in the position for supplying fluid to the circuit. Thesequence valve 94 creates, in the part of the circuit located upstreamof the valve, the establishment of a pressure which supplies theunlocking mechanism and the compensating mechanism. The four unlockingjacks 32 (FIG. 6) are supplied and this cancels out the force forlocking the saddle E with respect to the frame D exerted by the pullrods 32b.

It will be recalled that the compensating mechanism provided between thebed D and the saddle E is adapted to compensate the variable forces dueto the load carried by the table G. Indeed, these forces are essentiallyvariable as a function of the pivotal position of the chassis F and ofthe table G relative to the saddle E. The resultant of thesecompensating forces opposes the variable load both in intensity and inposition. This compensation is controlled by the pressure reducer 41 andthe pressure gauge 43 (FIG. 6). The three-position distributing valve 42controlled by the two position detectors 44, 45 shown in FIG. 1determine, in accordance with the pivotal position of the chassis F andof the table G, the jacks which exert the lightening or compensatingforces a. For a position of the table and chassis between and 45 (FIGS.1 and 6), the detector 44 energizes the electromagnet 42a of thedistributing valve 42 and shifts the slide of this valve in such mannerthat the lightening or compensation is effected on the three pairs ofmotors 35, 37 and 38 arranged over the lower face of the saddle E.

b. When the inclination of the saddle and chassis is between 45 and 60,the distributing valve 42 is in the neutral position shown in FIG. 6 andthe compensation is effected by the five pairs of jacks 34 to 38.

c. When the inclination of the table and chassis is between 60 and 90,the detector 45 energizes the electromagnet 42b of the distributingvalve 42 and shifts the slide of this valve in such manner that thecompensation is effected through the three pairs of jacks 34, 35 and 36adjacent the front of the saddle E.

It may be mentioned that the unit force of each lightening orcompensating jack 34 to 38 can be regulated between 0 and 4400 daN, forexample in accordance with the value of the load carried by the table G.

- As the unlocking and compensation are carried out automaticallyaccording to the pivotal position of the chassis and table, theservomotor 11 is supplied for operation in the desired direction so asto shift the saddle in one direction or the other by placing thedistributing valve 95 in the corresponding position. As alreadymentioned, the saddle is shifted with respect to the bed by theservomotor 11 through an assembly comprising a lead screw 10 and nut 9.The feed rates it is possible to obtain, in accordance with the chosenembodiment, from the feed mechanism have already been indicated.

There will now be described with reference to FIGS. 5, 7 and 9 themanner in which the table G is rotated with respect to the chassis Fabout the axis Z--Z. As in the preceding case, the circuit 91 issupplied with fluid by energizing the selecting valve 101 in such manneras to place it in its open position. The pressure which is establishedupstream of the sequence valve 102 is adapted to control the unlocking,lightening and weighting mechanisms (FIG. 7). The four unlocking jacks67 are supplied with fluid and this annuls the locking force exerted bythe pull rods 67b and disconnects the table G from the chassis F.

As in the case of the lightening on the bed, the lightening forceexerted by the jacks 69, and the weighting force exerted by the jacks 72between the table G and the chassis F depends on the inclination of thechassis and table with respect to the rest of the device. Thesecompensations in one direction and the other are adapted to oppose thevariable pivoting torque exerted by the load clamped to the table. Thepivotal position of the chassis and table determines which jacks mustproduce -a lightening and/0r weighting through the distributing valve 78having two electromagnets 78a, 78b,this valve being controlled by thetwo position detectors 44 and 45. Thus When the inclination of the tableis between 0 and 45 (FIG. 1), the detector 44 energizes theelectromagnet 78a. The lightening compensation is then effected by thetwo pairs of jacks 69 and 70 arranged on the chassis F. .1

When the inclination of the chassis is between 45 and 60, thedistributing valve 78 is in the neutral position. Only the two jacks 69which are the nearest to the pivot shaft 12 are supplied with fluid andexert a lightening effect.

When the inclination of the chassis is between 60 and which correspondsto the position in which the pivotating torque is the highest, thedetector 45 energizes the electromagnet 78b. The distributing valve 78is then placed in such position that the jacks 69 are still suppliedwith fluid to produce the lightening effect, the two jacks 72 also beingsupplied and exerting a weighting effect through levers, suchas thelever 74 (FIG. 5), and needle bearings 75 which bear against thehardened steel ring 73.

As in the case of the bed and saddle, the unit force of each lighteningjack and weighting jack can be adjusted between 0 and 4400 daN.

The table can be rotated about the axis Z--Z continuously at a speedvarying from 0.00072 rpm to 0.257 rpm for a continuous machining, orshifted angularly for positioning by increments whose minimum value is,for example, 0.00 1 5.

The pivoting of the assembly consisting of the chassis F and table Gcarrying the workpiece is controlled hydraulically in the followingmanner (FIGS. 8 and 9). With the valve placed in the position forsupplying fluid to the circuit, there is established upstream of thesequence valve 106 sufficient pressure to supply the jacks 65 and thusannul the locking force exerted by the pull rods 65b (FIG. 2).

There will first be explained the operation of the circuit 48 forrapidly pivoting the chassis F with respect to the saddle E. Assumingthat this chassis and the table are in the position shown in FIG. l,thatis, in the horizontal position, to pivot the chassis in the upwarddirection it is necessary to energize the distributing valve 50 in suchmanner that the slide of this valve moves toward the right as viewed inFIG. 8. The hydraulic fluid under pressure then passes through the valve50 and reaches the chambers 51 of the two jacks 46 through check valves53 and S4, 55. The fluid contained in the chambers 56 of the jacks canescape and return to the tank through check valves 59, 60 bearing inmind that these valves are piloted and maintained open.

At the beginning of this movement and as long as the inclination of thechassis is less than 45, the position detector 44 (FIG. 1) controls theelectromagnet of the valve 57 in such manner that the latter is open andthe fluid which escapes from the chambers 56 is not sub jected to aretaining counter-pressure. When the inclination of the chassis exceeds45, the retaining valve 57 is no longer piloted and acts as a functionof this adjustment so as to exert a counter-pressure which tends toretain the pivoting assembly and oppose the torque exerted by the load.

Likewise, in the course of the downward movement, for example from thevertical position shown in dotdash line in FIG. 1, if the slide of thedistributing valve 50 is shifted toward the left, as viewed in FIG. 8,the chambers 56 of the jacks 46 are supplied with fluid under pressurethrough the valves 58 and 59, 60, the fluid being able to escape fromthe chambers 51 since the check valves 54 and 55 are piloted andmaintained open. When the inclination of the table is between 60 and 90,the detector 45 controls the electromagnet of the valve 52 so that thisvalve opens and the fluid contained in the chambers 51 of the jacks isnot subjected to a counter-pressure. Beyond this inclination of 60, thatis between and 60, the retaining valve 52 is no longer piloted andexerts a regulated counter-pressure which tends to oppose the pivotingmovement of the movable assembly.

Thus, it can be seen that,owing to this device, a perfectly reliableoperation is ensured since a retention is automatically exerted when theload tends to having a driving effect.

The positioning circuit 49 operates in a simple manner the flowregulator 61 controls a low flow, the three-position distributing valve62 controls the fluid flow either in the direction of chambers 51 or inthe direction of the chambers 56, directly behind the check valves 54,55, 59 and 60.

By way of example, itmay be mentioned that the speeds of the pivotingmovement achieved through the circuit 48 and the circuit 49 arerespectively of the order of 90 per minute in respect of the rapid-feedcircuit 48 and from 9 per minute to 0.l2 per minute (namely 0.002 persecond) in respect of the positioning circuit 49. The angular positionof the pivoting assembly is controlled by a sighting arrangement whosereading precision is for example to within 001.

The device is completed by'a measuring and display unit (not shown)which enables the exact position of the various moving parts of thedevice to be measured and indicated to the user. The angular positionsof the pivotable chassis F and table G are determined for example towithin 0.0l whereas the position of the saddle with respect to the bedis measured with a precision of, for example, 0.01 millimeter.

It will be clear from the foregoing description of the operation thatthe workpiece support device according to the invention permitspositioning relative to the toolcarrying head of the machine a veryheavy workpiece, weighing for example as much as 25 metric tons. Thesemovements of the workpiece which result from the combination of threefeeds a transverse feed parallel to the axis XX, a pivotal feed aboutthe axis Y-Y and a rotational feed about the axis Z-Z permits theworkpiece to be brought into any required position, without dismountingor transferring the workpiece, for machining it on all its faces exceptthe face in contact with the table G. This device is therefore mostconvenient and is a considerable improvement over known support devices.

All the driving, locking, lightening and weighting mechanisms are sodesigned as to guarantee reliable operation.

Having now described our invention what we claim and desire to secure byLetters Patent is 1. A support device for machining a workpiececomprising a first pair of parts consisting of a first part defining afixed bed, a second part defining a saddle, interengaging guide meansinterposed between the saddle and the bed for supporting the saddle onthe bed for movement in a first direction, a second pair of partsconsisting of a third part defining a chassis mounted on the saddle topivot about a first axis substantially orthogonal to said firstdirection and a fourth part defining a table for receiving and holdingthe workpiece, interengaging guide means interposed between the tableand the chassis for supporting the table on the chassis for rotationabout a second axis substantially orthogonal to said pivot axis of thechassis, means for relatively moving said parts, releasable lockingmeans for maintaining said parts in desired positions relative to eachother, a plurality of hydraulically operated weight compensating meansin a plurality of spacedapart regions and interposed between parts ofone pair of said pairs of parts, each weight compensating means beingcapable of producing a relative steady force between the parts of saidone pair of parts, and hydraulic means for independently varying saidrelative force produced by each of the compensating means substantiallyas a function of forces exerted substantially in said regions throughsaid guide means of said one pair of parts due to the weight andposition of the workpiece relative to said one pair of parts so as tosubstantially balance said forces exerted by the workpiece.

2. A support device as claimed in claim 1, wherein said weightcompensating means comprise lightening means which comprise groups offluid cylinders fixed to one of the parts of said one pair of parts andhaving piston rods and rolling elements carried by the piston rods andadapted to bear and roll against a rolling face carried by the other ofthe parts of said one pair of parts, said relative forces produced bysaid lightening means being forces biasing the parts of said one pair ofparts away from each other.

3. A support device as claimed in claim 2, comprising five pairs oflightening fluid cylinders between the parts of said pair of parts.

4. A support device as claimed in claim 1, comprising between the saddleand the bed a plurality of lateral guiding and positioning meanscomprising rolling elements carried by the saddle and bearing against aguide face carried by the bed, said rolling elements being adjustablymounted on eccentrics so as to permit adjustment of pre-stressing of thelateral guiding of the saddle in its travel and permit a preciseadjustment of orthogonality between said first axis and said firstdirection.

5. A support device for machining a workpiece comprising a first partdefining a fixed bed, a second part defining a saddle, interengagingguide means interposed between the saddle and the bed for supporting thesaddle on the bed for'movement in a first direction, a third partdefining a chassis mounted on the saddle to pivot about a first axissubstantially orthogonal to said first direction, a fourth part defininga table for receiving and holding the workpiece, interengaging guidemeans interposed between the table and the chassis for supporting thetable on the chassis for rotation about a second axis substantiallyorthogonal to said pivot axis of the chassis, means for relativelymoving said parts, releasable locking means for maintaining said partsin given positions relative to each other, and a plurality ofhydraulically operated weight compensating means in a plurality ofspaced-apart regions and interposed between the chassis and the table,each weight compensating means being capable of producing a relativesteady force between the table and chassis, and hydraulic means forindependently varying said relative force produced by each of thecompensating means substantially as a function of forces exertedsubstantially in said regions through said guide means of the table andchassis due to the weight and position of the workpiece relative to saidtable and chassis so as to substantially balance said forces exerted bythe workpiece.

6. A support device as claimed in claim 5, wherein said weightcompensating means comprise lightening means comprising groups of fluidjacks fixed to one of the parts consisting of the chassis and the tableand having piston rods and rolling elements carried by the piston rodsand adapted to bear and roll against a rolling face carried by the otherof said parts consisting of the chassis and the table, said relativeforces produced by said lightening means being forces biasing the tableand chassis away from each other.

7. A support device as claimed in claim 5, wherein said weightcompensating means comprise at least two pairs of lightening fluid jacksinterposed between the chassis and the table, said relative forcesproduced by said lightening means being forces biasing the table andchassis away from each other.

8. A support device as claimed in claim 6, wherein said weightcompensating means comprise weighting means which comprise a pluralityof fluid jacks fixed to one of the parts consisting of the chassis andthe table and having piston rods, levers pivotably mounted on said oneof said parts consisting of the chassis and the table and having firstend portions respectively connected to the piston rods and second endportions, rolling elements respectively carried by the second endportions and a rolling face on the other of said parts consisting of thetable and the chassis ,said rollers bearing against said rolling faceand tending to urge the table against the chassis.

9. A support device for machining workpieces comprising a first partdefining a fixed bed, a second part defining a saddle mounted on the bedto be slidable in a first direction, a third part defining a chassismounted on the saddle to pivot about a first axis substantiallyorthogonal to said first direction, a fourth part defining a tablemounted on the chassis to be rotatable about a second axis substantiallyorthogonal to said pivot axis of the chassis, means for relativelymoving said parts, locking means for maintaining said parts in givenpositions relative to each other, and weight compensating meansinterposed between the chassis and the table and adapted to oppose theforces exerted by the weight of the workpiece carried by the table, theaction of said weight compensating means depending on the weight andposition of said workpiece and, in particular, on the pivotal positionof the chassis, said weight compensating means comprising lighteningmeans comprising groups of fluid motors fixed to one of the partsconsisting of the chassis and the table and having piston rods whichcarry rolling elements adapted to bear and roll against a rolling facecarried by the other of said parts consisting of the chassis and thetable, said weight compensating means further comprising weighting meanswhich comprise a pair of fluid .jacks fixed to one of the partsconsisting of the chassis and the table and having piston rods, leverspivotably mounted on said one of said parts consisting of the chassisand the table and having first end portions respectively connected tothe piston rods and second end portions, rolling elements respectivelycarried by the second end portions, a rolling face on the other of saidparts consisting of the table and the chassis, said rollers bearingagainst said rolling face and tending to urge the table against thechassis, means for supplying the weighting fluid jacks with fluid whenthe inclination of the chassis is at least to the horizontal.

10. A support device for machining workpieces comprising a first partdefining a fixed bed, a second part defining a saddle mounted on the bedto be slidable in a first direction, a third part defining a chassismounted on the saddle to pivot about a first axis substantiallyorthogonal to said first direction, a fourth part defining a tablemounted on the chassis to be rotatable about a second axis substantiallyorthogonal to said pivot axis of the chassis, means for relativelymoving said parts, locking means for maintaining said parts in givenpositions relative to each other and a mechanism pivoting the chassis tothe saddle comprising a shaft fixed with respect to the saddle andcarried by two supports having a tapered inner bearing face which isconvergent toward the middle of the shaft, the shaft carrying outsidesaid supports respectively two groups of two rolling bearings mounted inopposed relation and having outer bearing rings integral with thechassis.

11. A support device as claimed in claim 10, wherein in the region ofone of the supports the shaft has a corresponding tapered shape and, inthe region of the other of said supports, the shaft is cylindrical, asleeve having a cylindrical inner face and a tapered outer face beinginterposed between the shaft and said second support.

12. A support device for machining workpieces comprising a first partdefining a fixed bed, a second part defining a saddle mounted on the bedto be slidable in a first direction, a third part defining a chassismounted on the saddle to pivot about a first axis substantiallyorthogonal to said first direction, a fourth part defining a tablemounted on the chassis to be rotatable about a second axis substantiallyorthogonal to said pivot axis of the chassis, means for relativelymoving said parts, locking means for maintaining said parts in givenpositions relative to each other and three main hydraulic circuitsconnected in parallel with each other, a first of said circuits beingadapted to control the feed of the saddle with respect to the bed, asecond of said circuits being adapted to control the pivoting feed ofthe chassis with respect to the saddle, and a third of said circuitsbeing adapted to control the rotational feed of the table with respectto the chassis, each of said main circuits comprising in series aselecting valve, a sequence valve for establishing a regulated pressurevalue in the corresponding circuit and drive means for producing thecorresponding feed.

13. A support device as claimed in claim 12, wherein fluid supplycircuits for the locking means are branch connected to the main circuitsbetween the selecting valve and the sequence valve.

14. A support device for machining workpieces comprising a first partdefining a fixed bed, a second part defining a saddle mounted on the bedto be slidable in a first direction, a third part defining a chassismounted on the saddle to pivot about a first axis substantiallyorthogonal to said first direction, a fourth part defining a tablemounted on the chassis to be rotatable about a second axis substantiallyorthogonal to said pivot axis of the chassis, means for relativelymoving said parts, locking means for maintaining said parts in givenpositions relative to each other,weight compensating means interposedbetween the chassis and the table and adapted to oppose the forcesexerted by the weight of the workpiece carried by the table, the actionof said weight compensating means depending on the weight and positionof said workpiece and, in particular, on the pivotal position of thechassis,three main hydraulic circuits connected in parallel with eachother, a first of said circuits being adapted to control the feed of thesaddle with respect to the bed, a second of said circuits being adaptedto control the pivoting feed of the chassis with respect to the saddleand a third of said circuits being adapted to control the rotationalfeed of the table with respect to the chassis, each of said maincircuits comprising in series a selecting valve, a sequence valve forestablishing a regulated pressure value in the corresponding circuit,drive means for producing the corresponding feed,and supply circuits forthe locking means and weight compensating means branch connected to themain circuits between the selecting valve and the sequence valve.

15. A support device as claimed in claim 12, wherein the drive means forproducing the feed between the saddle and the bed, between the chassisand the saddle and between the table and the chassis respectively, areeach subjected to means responsive to pressure inserted in the maincircuit between the selecting valve and the sequence valve.

16. A support device as claimed in claim 13, comprising lightening meansinterposed between the bed and the saddle and adapted to oppose theforces exerted by the weight of the workpiece carried by the device, theaction exerted by said lightening means depending on the weight andposition of said workpiece and in particular on the pivot position ofthe chassis, said lightening means comprising fluid motors and fluidsupply circuits branch connected to the main-circuits between theselecting valve and the sequence valve and comprising in series apressure reducer and a threeposition distributing valve controlled by anelectric control.

17. A support device as claimed in claim 13, comprising weightcompensating means interposed between the chassis and. the table andadapted to oppose the forces exerted by the'weight of the workpiececarried by the table, the action of said weight compensating meansdepending on the weight and position of said workpiece and, inparticular, on the pivotal position of the chassis and said weightcompensating means comprising fluid motors and fluid supply circuitsbranch connected to the main circuits between the selecting valve andthe sequence valve and comprising in series a pressure reducer and athree-position distributing valve controlled by an electric control.

18. A support device as claimed in claim 16, comprising a conduit inparallel with the distributing valve which directlyly supplies at leastone group of lightening fluid motors.

19. A support device for machining workpieces comprising a first partdefining a fixed bed, a second part defining a saddle mounted on the bedto be slidable in a first direction, a third part defining a chassismounted on the saddle to pivot about a first axis substantiallyorthogonal to said first direction, a fourth part defining a tablemounted on the chassis to be rotatable about a second axis substantiallyorthogonal to sais pivot axis of the chassis, means for relativelymoving said parts, locking means for maintaining said parts in givenpositions relative to each other, and three main hydraulic circuitsconnected in parallel with each other, a first of said circuits beingadapted to control the feed of the saddle with respect to the bed, asecond of said circuits being adapted to control the pivoting feed ofthe chassis with respect to the saddle and a third of said circuitsbeing adapted to control the rotational feed of the table with respectto the chassis, each of said main circuits comprising in series aselecting valve,a sequence valve for establishing a regulatedpressurevalve in the corresponding circuit, drive means for producingthe corresponding feed, said drive means for pivoting the chassis withrespect to the saddle comprising two fluid motors respectively disposedon each side of the saddle, a rapid feedcircuit for supplying fluid tothe saddle fluid motors for rapid pivoting of the chassis with respectto the saddle and a slow feed circuit for supplying fluid to the saddlefluid motors for slowly pivoting the chassis with respect to the saddlefor positioning purposes.

20. A support device as claimed in claim 19, wherein the rapid feedcircuit comprises a three-position distributing valve having an electriccontrol and three branches respectively connecting said distributingvalve to two corresponding groups of chambers of the fluid motors, eachbranch comprising a non-piloted check valve and an electrically pilotedretaining valve connected in parallel, and two piloted check valvescontrolling an inlet and an outlet of the fluid for each of thechambers, the piloted retaining valves being placed in a return path ofthe fluid between said chambers and the distributing valve and adaptedto exert a counterthe slow-feed circuit comprises in series a flowregulator and a three-position distributing valve having an electriccontrol respectively connected to two branches of the rapid-feed circuitat points located between the chambers of the fluid motors and theassociated check valves.

22. A support device for machining a workpiece, comprising a first partdefining a fixed bed, a second part defining a saddle, guide meansinterposed between the saddle and the bed for supporting the saddle onthe bed for movement in a first direction, a third part defining achassis mounted on the saddle to pivot about a first axis substantiallyorthogonal to said first direction and a fourth part defining a tablefor receiving and holding the workpiece, guide means interposed betweenthe table and the chassis for supporting the table on the chassis forrotation about a second axis substantially orthogonal to said pivot axisof the chassis, hydraulic means for relatively moving the four parts,releasable locking means for maintaining said parts in desired positionsrelative to each other, a plurality of lightening means in a pluralityof spaced-apart regions and interposed between the saddle and the bedand between the table and the chassis, each lightening means beinghydraulic jack means capable of exerting a force in a direction forbiasing the saddle away from the bed and the table away from thechassis, and hydraulic control means connected to the hydraulic jackmeans for varying the force exerted by the jack means substantially as afunction of forces exerted substantially in said regions through saidfirst and second guide means due to the weight and position of theworkpiece relative to said four parts.

23. A device as claimed in claim 22, wherein said hydraulic controlmeans comprise position detecting means associated with the chassis andresponsive to changes in angular position of the chassis about saidfirst axis, hydraulic valve means for controlling actuation of said jackmeans and associated with said position detective means so that theangular position of the chassis about said first axis determines inwhich of said regions said hydraulic jack means are operative.

1. A support device for machining a workpiece comprising a first pair ofparts consisting of a first part defining a fixed bed, a second partdefining a saddle, interengaging guide means interposed between thesaddle and the bed for supporting the saddle on the bed for movement ina first direction, a second pair of parts consisting of a third partdefining a chassis mounted on the saddle to pivot about a first axissubstantially orthogonal to said first direction and a fourth partdefining a table for receiving and holding the workpiece, interengagingguide means interposed between the table and the chassis for supportingthe table on the chassis for rotation about a second axis substantiallyorthogonal to said pivot axis of the chassis, means for relativelymoving said parts, releasable locking means for maintaining said partsin desired positions relative to each other, a plurality ofhydraulically operated weight compensating means in a plurality ofspaced-apart regions and interposed between parts of one pair of saidpairs of parts, each weight compensating means being capable ofproducing a relative steady force between the parts of said one pair ofparts, and hydraulic means for independently varying said relative forceproduced by each of the compensating means substantially as a functionof forces exerted substantially in said regions through said guide meansof said one pair of parts due to the weight and position of theworkpiece relative to said one pair of parts so as to substantiallybalance said forces exerted by the workpiece.
 2. A support device asclaimed in claim 1, wherein said weight compensating means compriselightening means which comprise groups of fluid cylinders fixed to oneof the parts of said one pair of parts and having piston rods androlling elements carried by the piston rods and adapted to bear and rollagainst a rolling face carried by the other of the parts of said onepair of parts, said relative forces produced by said lightening meansbeing forces biasing the parts of said one pair of parts away from eachother.
 3. A support device as claimed in claim 2, comprising five pairsof lightening fluid cylinders between the parts of said pair of parts.4. A support device as claimed in claim 1, comprising between the saddleand the bed a plurality of lateral guiding and positioning meanscomprising rolling elements carried by the saddle and bearing against aguide face carried by the bed, said rolling elements being adjustablymounted on eccentrics so as to permit adjustment of pre-stressing of thelateral guiding of the saddle in its travel and permit a preciseadjustment of orthogonality between said first axis and said firstdirection.
 5. A support device for machining a workpiece comprising afirst part defining a fixed bed, a second part defining a saddle,interengaging guide means interposed between the saddle and the bed forsupporting the saddle on the bed for movement in a first direction, athird part defining a chassis mounted on the saddle to pivot about afirst axis substantially orthogonal to said first direction, a fourthpart defining a table for receiving and holding the workpiece,interengaging guide means interposed between the table and the chassisfor supporting the table on the chassis for rotation about a second axissubstantially orthogonal to said pivot axis of the chassis, means forrelatively moving said parts, releasable locking means for maintainingsaid parts in given positions relative to each other, and a plurality ofhydraulically operated weight compensating means in a plurality ofspaced-apart regions and interposed between the chassis and the table,each weight compensating means being capable of producing a relativesteady force between the table and chassis, and hydraulic means forindependently varying said relative force produced by each of thecompensating means substantially as a function of forces exertedsubstantially in said regions through said guide means of the table andchassis due to the weight and position of the workpiece relative to saidtable and chassis so as to substantially balance said forces exerted bythe workpiece.
 6. A support device as claimed in claim 5, wherein saidweight compensating means comprise lightening means comprising groups offluid jacks fixed to one of the parts consisting of the chassis and thetable and having piston rods and rolling elements carried by the pistonrods and adapted to bear and roll against a rolling face carried by theother of said parts consisting of the chassis and the table, saidrelative forces produced by said lightening means being forces biasingthe table and chassis away from each other.
 7. A support device asclaimed in claim 5, wherein said weight compensating means comprise atleast two pairs of lightening fluid jacks interposed between the chassisand the table, said relative forces produced by said lightening meansbeing forces biasing the table and chassis away from each other.
 8. Asupport device as claimed in claim 6, wherein said weight compensatingmeans comprise weighting means which comprise a plurality of fluid jacksfixed to one of the parts consisting of the chassis and the table andhaving piston rods, levers pivotably mounted on said one of said partsconsisting of the chassis and the table and having first end portionsrespectively connected to the piston rods and second end portions,rolling elements respectively carried by the second end portions and arolling face on the other of said parts consisting of the table and thechassis ,said rollers bearing against said rolling face and tending tourge the table against the chassis.
 9. A support device for machiningworkpieces comprising a first part defining a fixed bed, a second partdefining a saddle mounted on the bed to be slidable in a firstdirection, a third part defining a chassis mounted on the saddle topivot about a first axis substantially orthogonal to said firstdirection, a fourth part defining a table mounted on the chassis to berotatable about a second axis substantially orthogonal to said pivotaxis of the chassis, means for relatively moving said parts, lockingmeans for maintaining said parts in given positions relative to eachother, and weight compensating means interposed between the chassis andthe table and adapted to oppose the forces exerted by the weight of theworkpiece carried by the table, the action of said weight compensatingmeans depending on the weight and position of said workpiece and, inparticular, on the pivotal position of the chassis, said weightcompensating means comprising lightening means comprising groups offluid motors fixed to one of the parts consisting of the chassis and thetable and having piston rods which carry rolling elements adapted tobear and roll against a rolling face carried by the other of said partsconsisting of the chassis and The table, said weight compensating meansfurther comprising weighting means which comprise a pair of fluid jacksfixed to one of the parts consisting of the chassis and the table andhaving piston rods, levers pivotably mounted on said one of said partsconsisting of the chassis and the table and having first end portionsrespectively connected to the piston rods and second end portions,rolling elements respectively carried by the second end portions, arolling face on the other of said parts consisting of the table and thechassis, said rollers bearing against said rolling face and tending tourge the table against the chassis, means for supplying the weightingfluid jacks with fluid when the inclination of the chassis is at least60* to the horizontal.
 10. A support device for machining workpiecescomprising a first part defining a fixed bed, a second part defining asaddle mounted on the bed to be slidable in a first direction, a thirdpart defining a chassis mounted on the saddle to pivot about a firstaxis substantially orthogonal to said first direction, a fourth partdefining a table mounted on the chassis to be rotatable about a secondaxis substantially orthogonal to said pivot axis of the chassis, meansfor relatively moving said parts, locking means for maintaining saidparts in given positions relative to each other and a mechanism pivotingthe chassis to the saddle comprising a shaft fixed with respect to thesaddle and carried by two supports having a tapered inner bearing facewhich is convergent toward the middle of the shaft, the shaft carryingoutside said supports respectively two groups of two rolling bearingsmounted in opposed relation and having outer bearing rings integral withthe chassis.
 11. A support device as claimed in claim 10, wherein in theregion of one of the supports the shaft has a corresponding taperedshape and, in the region of the other of said supports, the shaft iscylindrical, a sleeve having a cylindrical inner face and a taperedouter face being interposed between the shaft and said second support.12. A support device for machining workpieces comprising a first partdefining a fixed bed, a second part defining a saddle mounted on the bedto be slidable in a first direction, a third part defining a chassismounted on the saddle to pivot about a first axis substantiallyorthogonal to said first direction, a fourth part defining a tablemounted on the chassis to be rotatable about a second axis substantiallyorthogonal to said pivot axis of the chassis, means for relativelymoving said parts, locking means for maintaining said parts in givenpositions relative to each other and three main hydraulic circuitsconnected in parallel with each other, a first of said circuits beingadapted to control the feed of the saddle with respect to the bed, asecond of said circuits being adapted to control the pivoting feed ofthe chassis with respect to the saddle, and a third of said circuitsbeing adapted to control the rotational feed of the table with respectto the chassis, each of said main circuits comprising in series aselecting valve, a sequence valve for establishing a regulated pressurevalue in the corresponding circuit and drive means for producing thecorresponding feed.
 13. A support device as claimed in claim 12, whereinfluid supply circuits for the locking means are branch connected to themain circuits between the selecting valve and the sequence valve.
 14. Asupport device for machining workpieces comprising a first part defininga fixed bed, a second part defining a saddle mounted on the bed to beslidable in a first direction, a third part defining a chassis mountedon the saddle to pivot about a first axis substantially orthogonal tosaid first direction, a fourth part defining a table mounted on thechassis to be rotatable about a second axis substantially orthogonal tosaid pivot axis of the chassis, means for relatively moving said parts,locking means for maintaining said parts in given posItions relative toeach other,weight compensating means interposed between the chassis andthe table and adapted to oppose the forces exerted by the weight of theworkpiece carried by the table, the action of said weight compensatingmeans depending on the weight and position of said workpiece and, inparticular, on the pivotal position of the chassis,three main hydrauliccircuits connected in parallel with each other, a first of said circuitsbeing adapted to control the feed of the saddle with respect to the bed,a second of said circuits being adapted to control the pivoting feed ofthe chassis with respect to the saddle and a third of said circuitsbeing adapted to control the rotational feed of the table with respectto the chassis, each of said main circuits comprising in series aselecting valve, a sequence valve for establishing a regulated pressurevalue in the corresponding circuit, drive means for producing thecorresponding feed,and supply circuits for the locking means and weightcompensating means branch connected to the main circuits between theselecting valve and the sequence valve.
 15. A support device as claimedin claim 12, wherein the drive means for producing the feed between thesaddle and the bed, between the chassis and the saddle and between thetable and the chassis respectively, are each subjected to meansresponsive to pressure inserted in the main circuit between theselecting valve and the sequence valve.
 16. A support device as claimedin claim 13, comprising lightening means interposed between the bed andthe saddle and adapted to oppose the forces exerted by the weight of theworkpiece carried by the device, the action exerted by said lighteningmeans depending on the weight and position of said workpiece and inparticular on the pivot position of the chassis, said lightening meanscomprising fluid motors and fluid supply circuits branch connected tothe main circuits between the selecting valve and the sequence valve andcomprising in series a pressure reducer and a three-positiondistributing valve controlled by an electric control.
 17. A supportdevice as claimed in claim 13, comprising weight compensating meansinterposed between the chassis and the table and adapted to oppose theforces exerted by the weight of the workpiece carried by the table, theaction of said weight compensating means depending on the weight andposition of said workpiece and, in particular, on the pivotal positionof the chassis and said weight compensating means comprising fluidmotors and fluid supply circuits branch connected to the main circuitsbetween the selecting valve and the sequence valve and comprising inseries a pressure reducer and a three-position distributing valvecontrolled by an electric control.
 18. A support device as claimed inclaim 16, comprising a conduit in parallel with the distributing valvewhich directlyly supplies at least one group of lightening fluid motors.19. A support device for machining workpieces comprising a first partdefining a fixed bed, a second part defining a saddle mounted on the bedto be slidable in a first direction, a third part defining a chassismounted on the saddle to pivot about a first axis substantiallyorthogonal to said first direction, a fourth part defining a tablemounted on the chassis to be rotatable about a second axis substantiallyorthogonal to sais pivot axis of the chassis, means for relativelymoving said parts, locking means for maintaining said parts in givenpositions relative to each other, and three main hydraulic circuitsconnected in parallel with each other, a first of said circuits beingadapted to control the feed of the saddle with respect to the bed, asecond of said circuits being adapted to control the pivoting feed ofthe chassis with respect to the saddle and a third of said circuitsbeing adapted to control the rotational feed of the table with respectto the chassis, each of said main circuits comprising in series aselecting valve,a sequence valve for establishing A regulated pressurevalve in the corresponding circuit, drive means for producing thecorresponding feed, said drive means for pivoting the chassis withrespect to the saddle comprising two fluid motors respectively disposedon each side of the saddle, a rapid feedcircuit for supplying fluid tothe saddle fluid motors for rapid pivoting of the chassis with respectto the saddle and a slow feed circuit for supplying fluid to the saddlefluid motors for slowly pivoting the chassis with respect to the saddlefor positioning purposes.
 20. A support device as claimed in claim 19,wherein the rapid feed circuit comprises a three-position distributingvalve having an electric control and three branches respectivelyconnecting said distributing valve to two corresponding groups ofchambers of the fluid motors, each branch comprising a non-piloted checkvalve and an electrically piloted retaining valve connected in parallel,and two piloted check valves controlling an inlet and an outlet of thefluid for each of the chambers, the piloted retaining valves beingplaced in a return path of the fluid between said chambers and thedistributing valve and adapted to exert a counter-pressure tending tooppose the return of said fluid under predetermined conditions and inparticular when the effect of the weight of the workpiece on the chassisand the table tends to accentuate the pivoting movement, and piloted byposition detectors actuated by the chassis to open and no longer exertsaid counter-pressure when the effect of the weight of the workpiecetends to oppose the pivoting movement produced by the fluid motors. 21.A support device as claimed in claim 20, wherein the slow-feed circuitcomprises in series a flow regulator and a three-position distributingvalve having an electric control respectively connected to two branchesof the rapid-feed circuit at points located between the chambers of thefluid motors and the associated check valves.
 22. A support device formachining a workpiece, comprising a first part defining a fixed bed, asecond part defining a saddle, guide means interposed between the saddleand the bed for supporting the saddle on the bed for movement in a firstdirection, a third part defining a chassis mounted on the saddle topivot about a first axis substantially orthogonal to said firstdirection and a fourth part defining a table for receiving and holdingthe workpiece, guide means interposed between the table and the chassisfor supporting the table on the chassis for rotation about a second axissubstantially orthogonal to said pivot axis of the chassis, hydraulicmeans for relatively moving the four parts, releasable locking means formaintaining said parts in desired positions relative to each other, aplurality of lightening means in a plurality of spaced-apart regions andinterposed between the saddle and the bed and between the table and thechassis, each lightening means being hydraulic jack means capable ofexerting a force in a direction for biasing the saddle away from the bedand the table away from the chassis, and hydraulic control meansconnected to the hydraulic jack means for varying the force exerted bythe jack means substantially as a function of forces exertedsubstantially in said regions through said first and second guide meansdue to the weight and position of the workpiece relative to said fourparts.
 23. A device as claimed in claim 22, wherein said hydrauliccontrol means comprise position detecting means associated with thechassis and responsive to changes in angular position of the chassisabout said first axis, hydraulic valve means for controlling actuationof said jack means and associated with said position detective means sothat the angular position of the chassis about said first axisdetermines in which of said regions said hydraulic jack means areoperative.